This is a novel of sheer genius. It was first published in 1978 and it may have dropped below the horizon by now, but in the unlikely event that anyone reads this review I am only too happy to take the opportunity to draw some attention back to it.
Regarding the author, I remember her very well from a brilliant TV series that she wrote featuring a young agony-aunt called, as I recall, Jane, who lived in what she and her husband liked to call an open marriage. Those were the days my friends we thought would never end. They were an era of compulsory enlightenment featuring every kind of noisy, arrogant and self-publicising political affectation, although of course there were other aspects to it all that were of more significance. In particular the heyday of the women's movement was not far behind us, and although Emma Tennant was usually discussed as being aligned with that, her TV series showed a very pleasant tongue-in-cheek detachment as well as real originality and humour.
The Bad Sister is about a very different Jane. Two very different styles of writing are used, and Jane's strange journal that constitutes the central and main section of the book is likely to put more strain on your concentration (and maybe your tolerance too) than the first part, which reads very enticingly as the start of a murder mystery with, possibly, a supernatural tinge to it. It ends with more than simply a tinge of that, just at the point where the story has reverted to what might be called approximately the rational level. In between we have Jane's journal, and we are cast adrift on a strange dark sea of phantasmagory. Reality as normally understood keeps making an appearance of course, otherwise the more fantastic and mysterious dimensions would be less fantastic and less mysterious. What kicks off this story-within-a-story is Jane's involvement with a grotesque radical-feminist commune, majoring in the cod-Marxism that was so popular at the time, and I can't help sensing that the comment, put into the mouth of Jane, is Emma Tennant's own `My sisters had been nightmares...black bats of uncertainty and loneliness and despair.'
After the black bats have flown the theme of possession and seeking power over others becomes dominant, sometimes in surprising and unexpected contexts, always in dark and mysterious movements. If Lovecraft had not commandeered the term `dream-quest' it would suit the narrative here very well, but this is writing and imagination completely out of Lovecraft's depth. The `shell' narrator at the start is at pains to make it clear that the supposed murderer seems to have disappeared entirely, but the final denouement is a stroke of real dark brilliance, and I can only suppose it would have excited the envy of M R James himself. If you find Jane's journal a bit of a struggle, I promise you that it is worth struggling through for the sake of this final incident alone. In any case the book is not long. Some editions manage to make it occupy 400-odd pages, heaven knows how. My own edition runs to all of 142, about the length of your average novel by Muriel Spark. Here, for sheer quality, is a production that rivals Spark and that for sinister fantasy is in another category.